Accreditation has become a widespread tool for quality control and development, and large resources are spent upon development and implementation of accreditation systems in health care systems all over the world. Accreditation of healthcare systems has met some critique. Evidence for positive effects of accreditation has been called for, and health care professionals have expressed concerns about extra hours imposed by accreditation. However, only few studies have evaluated the effects of accreditation on central items, such as clinical outcomes and patient satisfaction. In general, the results from the different types of studies are ambiguous and there are only few well-accomplished effect studies. Hence, only two effect studies met the methodological inclusion criteria of a recent Cochrane review. None of these studies treated general practice. A review regarding status of accreditation in primary care concluded that there is a dearth of research on the nature and uptake of accreditation in this sector along with how accreditation affects outcomes of care, and whether it is an effective method to improve quality, perceptions of care, healthcare utilisation and costs. Two studies provided evidence to suggest that accreditation status was associated with infection control procedures, risk management programmes and quality improvement activities and after-treatment plans. However, in the latter case, post hoc analysis revealed that accreditation was associated with units' organizational contexts and referral sources as well as the nature of the competitive environment. The authors concluded that accreditation and licensing might reveal as much about a care units' institutional environments as about the quality of treatment provided. Accreditation is a relatively new instrument in general practice and its effects on clinical outcomes, patient satisfaction, general practitioners' (GPs') job satisfaction and organisational aspects must be evaluated in order to assess the overall utility for patients and society. Although accreditation has been implemented in general practice in nine European countries, and in Australia and New Zealand, research elucidating the effects of accreditation in general practice system, is strongly needed. In spite of this lack of evidence for effect of accreditation on clinical and patient related objectives, it has been decided to implement accreditation as a mandatory instrument in Danish general practice.